#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
    int n = 0;
    int num = 0;
    int ret = 0;
    scanf("%d", &n);
    for (int i = 0; i < n; ++i)
    {
        scanf("%d", &num);
        ret ^= num;
    }
    printf("%d ", ret);
}
